It has long been known for aircraft to be provided, in the lower region, with what are known as crash boxes, which in the case of an emergency landing convert the kinetic energy of the aircraft hitting the ground into deformation work.
It is described in DE 601 14 455 T2 to flatten the annular fuselage frame in the lower region of the fuselage and to provide, below this flattened horizontal frame portion, beams which extend in the longitudinal direction and are designed as energy-absorbing composite beams. These composite beams are mounted on the horizontal frames by means of fastening fittings. These fastening fittings significantly increase the total weight of the aircraft and, if they are made for example of titanium in order to reduce the weight, considerably increase the production costs of the aircraft. In addition, in this region the frames are connected to the fuselage skin only via the deformable longitudinal beams, and therefore, when a transverse force component occurs in the case of a vertical impact of the aircraft, it is to be expected that the deformable longitudinal beams give way laterally.
DE 44 16 506 A1 describes an aircraft fuselage which is provided in its lower region with a lower floor structure which is supported by means of support elements which extend obliquely to the vertical longitudinal centre plane of the aircraft between the lower floor structure and the fuselage frames. Below the lower floor structure, a deformation structure is provided on the outside of the fuselage and considerably increases the aerodynamically effective cross-section of the aircraft.
If beams which are part of an energy-absorbing deformation structure are provided in the lowest region of the fuselage, between a lower floor and the frames, then these beams can convert kinetic energy into deformation energy in the case of an impact on solid ground. However, there is a risk of shear forces occurring in the region in which these beams are mounted on the fuselage frames, which forces can lead to tearing of the fuselage skin or even of the frame in this region in the case of an impact. In the case of an emergency landing on water, water may then undesirably enter the fuselage.
An impulse-absorbing structural component developed by the inventor of the present application is described DE 10 2007 038 634 B3. This structural component consists of an impulse-absorbing layer on which a covering layer is mounted. The impulse-absorbing layer has a regular pattern of elevations and depressions such that, should a mass part impact on the covering layer, an intercept bag forms in the impulse-absorbing layer and dissipates the kinetic energy of the mass part.